If your looking for something that can last, you could look into something like this:
Duracoat Aerosol
It's a one time (48 hour) use can, but looks very cool. I'd probably look to do all your mags at once and maybe any accessories you want OD as well.
I've heard you want to mask off and only paint what sticks out so you don't add extra thickness to the mag in the magwell. Plus I'd strip them down and do all the parts separate and shove some news paper or paper towels in the mag to keep the insides nice and clean for smooth feeding.
Good luck and wouldn't mind seeing what you come up with.